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Re: Tributary Area

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I have always used half.  If a series of girders are in line, each gets half of the adjacent spans the same as in load distribution.  Same is true for columns.
Where it gets interesting is when you have continuous systems; is the live load reduction based on the smallest tributary single span, the average tributary on a single span, some multiple of spans rationalized on re-distribution, or the entire continuous run in which case it is always the maximum permitted reduction by default?
----- Original Message -----
Sent: Thursday, August 11, 2005 9:20 AM
Subject: Tributary Area

What is the precise definition of Tributary Area for figuring live load reduction?  The UBC defines it as the area of floor or roof supported by the member.  If a beam supports one edge of a simple-span floor, is the tributary areas the span of the beam times width of the floor, or is it half that area because the beam supports only half the floor [the other half is supported on the other edge]?  I?ve seen it done both ways, and have done it both ways myself.


Nels Roselund, SE

South San Gabriel, CA